Aviation turbo fuel



p 29, 190 T. B. WASSERBACH ETAL 2,952,969

AVIATION TURBO FUEL Filed May 26, 1955 G EG m M 8 rl v 0 m m h in He C nG nj W0 r w l 8% h of y E B a TM Patented Sept. 20, 1960 AVIATION TURBOFUEL Theodore B. Wasserbach, Cranford, and Matthew W. France, Elizabeth,N..I., assignors to Esso Research and Engineering Company, a corporationof Delaware Filed May 26, 1955, Ser. No. 511,261

6 Claims. (Cl. 60-35.4-)

The present invention is concerned with an improved" aviation fuel andin particular with a turbo jet fuel that will not plug the filters inairplane fuel systems at relatively low temperatures. The invention ismore particularly concerned with an improved method of operating a jetpropelled aircraft by utilizing the jet fuel composition of the presentinvention. The present application is a continuation-in-part ofapplication Serial No. 205,216, filed January 9, 1951, for Wasserbaeh etal., entitled Aviation Turbo Fuel, and now abandoned.

In accordance with the present invention improved high quality turbo jetfuels are secured by utilizing a particular addition agent which isselected from the class of compounds represented by the formula whereinx and y are integers, wherein X represents a residue of a polyhydricalcohol and R represents a hydrocarbon group having from 11 to 21 carbonatoms per molecule. Preferred compounds are mono-oleates, for examplesorbitan mono-oleate and its polyether derivatives produced by reactingsorbitan mono-oleate with ethylene oxide. A particularly desirablemono-oleate comprises polyethylene glycol mono-oleate wherein x equals6; y equals 1 and which compound is represented by the formula It iswell known in the art to utilize various types of turbo jet fuels.However, one of the most severe limita tions to maximum availability ofturbo fuel is the freezing point specification which is considerednecessary in order to insure fuel flow under high altitude, lowtemperature conditions. In order to provide fuels that have very lowfreezing points, various processes such as solvent extraction and thelike have been suggested. On the other hand, it has been found that attemperatures well above the specified hydrocarbon freezing point,difiiculties such as plugging of fuel filters, are often encountered dueto freezing out of dissolved or entrained water. In a normal type ofturbo jet engine, compressed air is passed into a combustion chamberwherein fuel under pressure is injected into the flowing air. This fuelis introduced by means of a pump. Prior to passing the fuel through thepump the fuel is passed through a micronic or equivalent type filterwhich is necessary in order to protect the fuel nozzle. Under lowtemperature conditions ice from water dissolved or entrained in the fuelforms on the filter, causing fuel flow failure and engine stoppage. Ithas, however, now been discovered that when a certain class of compoundsare added, unexpected desirable results are secured with respect to thisproblem of icing of the filter.

The additive anti-icing agents of the present invention are selectedfrom the class of compounds represented by the formula wherein x is aninteger between 1 and 10, y is an integer one less than the number ofhydroxy groups in a polyhydric alcohol which has two to six hydroxygroups and of which X represents the residue radical, and R repre sentsa hydrocarbon group having from 11 to 21 carbon atoms. Very desirableagents comprise sorbitan mono acid esters and in particular thepolyoxyethylene ethers thereof, which compounds are produced by reactingsorbitan mono acid esters with ethylene oxide in accordance with thefollowing:

0 H H om on-omooon I l +"N"HC CH HO-CH onon \0/ onon ornonloo on onoong-onl-om-n on-ocnrom-om-n no-onl-onom-o-om-on-o onl-onz-o) 3-Hwherein R represents the hydrocarbon radical of a relatively long chain(C to C fatty acid, as for example lauric, palmitic, oleic, stearic orbehenic acid, or mixtures thereof. The preferred compounds are themono-oleates. The polyoxy ethylene ethers of sorbitan mono-oleatepreferably contain from 2 to 10 carbon atoms in each ether radical.Other desirable additives are polyethylene glycol derivatives of longchain fatty acids represented by the formula wherein at and R have thesame meaning as above. These compounds can be prepared by esterifyingone mole of polyethylene glycol withone mole of a fatty acid. Aparticularly desirable compound is the polyethylene glycol ester ofoleic acid having the formula The present invention may be readilyunderstood by the following examples illustrating the same.

EXAMPLE I the filter until plugging occurred. The results are shown inTable I.

plugging tendencies of hydrocarbon fuels Table I.-- Efiect of additiveson the low temperature filter [Fuels Water saturated at roomtemperature, 2 gallon fuel charge-0.05 wt. percent additive, micronSkinner'paper type-filter] Fuel, Vol. Fercent..- 90 lileptanello TolueneFuel Freezing Pt..

Turbo Fuel Additive No e (1) 2 Time to Plugging,

Min.:

Additive added to fuel just prior to run 9 Fuel containing additivestood 7 over water for 24 None None

M About 0.005 v01. percent. 7

" U.S. Specification MIL 5624.

1 Polyoxyethylene ethers of sorbitan mono-oleate (containing 4oxyethylene groups). 2 Polyoxyethylene derivative of long chain fattyacid (oleic acid) (containing 6 oxyethy lene groups).

Time in minutes to the moment at which desired flow rate of 150 cc. perminute could not be maintained with a pressure of 22 ins. of mercuryabsolute. 4 Fuel agitated periodically with water. Thus, it is evidentfrom the above that plugging of engine filters due to the freezing outof dissolvedwater can be prevented by using the additives of the presentinvention. These additives have the unusual advantage over' other activeagents that these materials can be added to fuel at a refinery sourcewithout bringing excess water into the fuel due to storage over waterfor prolonged periods.

EXAMPLE H Sorbitan mono-oleate was also found to be an effectiveanti-icing agent, as will be observed from the data shown in thefollowing table:

Table II.Efiect of surface active agents on the plugging of turbo enginefuel filters due to the freezing out of dissolved water [10 micron woolyarn filter, 0.4 square inch area, flow rate of 150 cc./

minute at F. fuel temperature] Fuel Heptane (water saturated at roomtemp.). Additive Nmm Sorbitan monooleate.

Concentration, Wt. Percent.--

Time to Plugging, Mins 13 (Aver. of 3 runs).

After standing over water for 9.

24 hrs.

It will be observed, however, that for maximum effectiveness, thisparticular agent should be employed in fuelswhich are to be stored indry tanks.

EXAMPLE III .A number of operations were conducted using variousconcentrations of sorbitan mono-oleate in a fuel for the prevention offilter icing at -20 F. The results of these tests are as follows:

Sorbitan Time to plug mono-oleate filter, wt. percent: 7 minutes None 90.01 14 0.05 7 46 0.08 46 From the above data it is evident that theamount of additive used may vary appreciably but is in the range from0.02 to 0.2% by weight. Preferred concentrations are in the range from0.05 to 0.1% by weight.

These additives are adapted particularly for low temperature turbo jetfuels boiling generally in therange 0.02. 46 (no plugging).

from about 100 to 600 F. lln general, these fuels comply with the JP-1and JP-3 grades of U8. Specification MIL-F-56l6 and 5624 respectively.-They are also applicable toother fuels particularly IP-4, which has 2.to 3 p.s.i.a. Reid vapor pressure. These fuels may all be employed inram-jet engines as well as in turbo-jets.

Some typical inspections of these fuels are:

J P-1 J P-3 Aromatics, Vol. percent 20 25 Gravity, API 35 45-63 Reid vr.#/Sq. In. 5.0-7.0 ASTM Distillation (at 4-5 cc./Min.):

Resid. After Dist., percent These turbo-jet fuels are petroleum naphthasless volatile than gasoline and more volatile than heating oil, dieselfuel or other fuel oils. For instance, gasoline typically has a Reidvapor pressure of at least 6 and preferably above 7 p.s.i.a., an initialboiling-point of 90 F. and an end-point of 420 F. by ASTM method D-86;and heating oil typically has a flash-point above 150 F.,

an initial boiling point of 390 F. and an end-point 0f- 675 F.; but JP-3has an initial boiling point of about processes.

150 F. and an end-point of 540 F. The volatility limitations ofturbo-jet fuel are critical at the flash-point and at the point in thedistillation. The flash-point is below F. for the least volatile grade,JP-l, and the 90% pointmust be between 400 F. and 490 F.; whereasgasoline has its 90% point below 365 F. and preferably below 356 F. asmay be seen in specifications in MTLG 3056 and VV-M-561 of United StatesDepartment of Defense and Federal Supply Service respectively.

Turbo-jet fuels are required to be completely free of this invention isevident from the accompanying drawing in which the single figure shows adiagrammatical sketch of a jet turbine engine. Air is introduced intoengine 1 through air compressor 2. The compressed air flows into thecombustion chamber 5 wherein it is mixed with fuel introduced by meansof lines 4. The fuel filters are installed in lines 4, which terminatein spray-nozzles. The hot gases flow through turbine 7 and are jettedthrough tail-pipe 8 as shown.

What is claimed is:

1. The method of operating the jet engine of a jet propelled aircraft atlow temperatures which comprises operating said engine with ahydrocarbon jet fuel containing from 0.02 to 0.2 weight percent of acompound selected from the class consisting of the sorbitan monoesters,the polyoxyethylene ethers of the sorbitan monoesters,

and the polyethylene glycol. monoesters, of fatty acids having from 12to 22 carbon atoms, whereby ice formation and resultant fuel filterplugging within the fuel system of said engine are prevented.

2. A fuel composition for use in a jet engine which consists of amixture of hydrocarbons boiling within the range of from about 100 F. to600 F. and containing from 0.02 to 0.2 weight percent of a compoundselected from the class consisting of the sorbitan monoesters, thepolyethylene glycol monoesters, and the polyoxyethylene ethers of thesorbitan monoesters, of fatty acids having from 12 to 22 carbon atoms.

3. Fuel composition as defined by claim 2 wherein said compound isemployed in a concentration within the range of from 0.05 to 0.1 percentby weight.

4. A fuel composition for use in a jet engine which consists of amixture of hydrocarbons boiling within the range of from about to 600 F.and containing from 0.02 to 0.2 wt. percent of a sorbitan mono-oleate.

5. A fuel composition for use in a jet engine which consists of amixture of hydrocarbons boiling within the range of from about 100 to600 F. and containing from 0.02 to 0.2 wt. percent of a polyethyleneglycol monooleate.

6. A fuel composition for use in a jet engine which consists of amixture of hydrocarbons boiling within the range of from about 100 to600 F. and containing from 0.02 to 0.2 wt. percent of a polyoxyethyleneether of a sorbitan mono-oleate.

References Cited in the file of this patent UNITED STATES PATENTS2,548,347 Caron et a1. Apr. 10, 1951 2,599,338 Lifson et a1. June 3,1952 2,858,201 Newman Oct. 28, 1958 OTHER REFERENCES Murray: The Oil andGas Journal, Mar. 29, 1951, pages 218, 219, 271-281.

1. THE METHOD OF OPERATING THE JET ENGINE OF A JET PROPELLED AIRCRAFT ATLOW TEMPERATURES WHICH COMPRISES OPERATING SAID ENGINE WITH AHYDROCARBON JET FUEL CONTAINING FROM 0.02 TO 0.2 WEIGHT PERCENT OF ACOMPOUND SELECTED FROM THE CLASS CONSISTING OF THE SORBITAN MONOESTERS,THE POLYOXYETHYLENE ETHERS OF THE SORBITAN MONOESTERS, AND THEPOLYETHYLENE GLYCOL MONOESTERS, OF FATTY ACIDS HAVING FROM 12 TO 22CARBON ATOMS, WHEREBY ICE FORMATION AND RESULTANT FUEL FILTER PLUGGINGWITHIN THE FUEL SYSTEM OF SAID ENGINE ARE PREVENTED.